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Carbon nanotubes (CNTs) are prepared by the hot filament chemical vapour deposition method using CH₄ and H₂ as reaction gases and the growth behaviours are investigated by scanning electron microscopy and transmission electron microscopy. The results indicate that the CNTs prepared in the absence of N₂ or glow discharge are bent; however, they are in an aligned state after introducing N₂ into the chamber or forming glow discharge under a negative biased voltage. The results also indicate that the CNTs are of a bamboo-like structure when N₂ is intruded as a reaction gas and the alignment degree of the CNTs grown under glow discharge is higher than that grown in N₂. This illustrates that the nitric environment and glow discharge play important roles in the growth of CNTs. Combining with the theory related to alloy thermodynamics and collisions, we have analysed the growth mechanism of the CNTs in nitric environment and glow discharge.